Export noise textures as image
Create a default plane (2x2 BU), assign your material; in object mode, material tab, click on the number near the material name to create a copy of it, delete the diffuse shader and put an emission shader instead, take the displacer input and put it on the color input; select the camera, Alt G, Alt R, to reset its trasform values, move it up in z axis a little, set it to orthographic mode, orthographic scale 2 and 2048 x 2048 dimension (or whatever you need). 

F12 with no lights.